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Old Aug 14, 2003, 09:30 AM
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Some interesting reading for those looking for the "facts".

Do a Google search on "Lithium Polymer Battery Fire"

Just a couple to read further:

DOT Proposed Regulation on Transportation of Lithium Batteries

http://hazmat.dot.gov/rules/2002_11989.htm

ASC 2001 Training Workshop on Batteries

http://www.formulasun.org/asc/tech/b...1_Workshop.pdf

another one on the need for a protection circuit

http://www.littelfuse.com/PDFs/AppNotes/ec611.pdf

another on the need for a "fire retardant" in Lithium batteries

http://www.sciencenews.org/20000212/fob6.asp

The facts are there, you just have to want to look....


Brad
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Old Aug 14, 2003, 09:47 AM
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Thanks Brad
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Old Aug 14, 2003, 10:29 AM
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Sorry, somehow that message posted twice.

Brad
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Old Aug 14, 2003, 11:40 AM
Build'em and Crash'em
Ken Lapointe's Avatar
Narragansett, RI
Joined Oct 2000
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Great thread

This is really good information and has opened my eyes a bit on changing over to Li-Poly packs.

I think the chargers and packs need a better way to sync up with the cell voltage and number of cells. In this day and age why can't I put come kind of chip on my pack or RF tag that tells the charger the number of cells? It can't be that hard. And don't complain about the price going up, we are willing to pay $300 for a pack.

One thing I would say is that the packaging for Li-Poly is wrong for R/C. Think about that NiCad or NimH cell. Things don't get much stronger than a metal cylinder. I would gladly give up the weight benefit for a safer pack. How about some Kevlar material to prevent the sparks from going everywhere. Not a sealed bag but some kind of containment bag. Maybe something better than folded over metal tabs just waiting to puncture thin plastic outer wrapping.

I keep reading that folks suggest that you should check the packs for damage before putting in the car after your crash. What are you really checking for? How do you know nothing will happen after you put them in the car? When can you feel safe with them if you even drop them on the floor?

Can someone explain to me what happens when you have a momentary short circuit? Does it cause a fire problem or just damage the pack in some way? How long is momentary? 1/2 a sec, 4 seconds.....?

The crash damage issue is what really worries me. Sooner or later I crash my planes. Sometimes the crash is worse than others. What is the level of damage I have to worry about?

With Li-Poly packs now I would need a safe charging area, a fire safe transport box, a bucket of salt water and a fire extinguisher. Tell me again why I fly electric planes over glow power?


What about charging at the field, what happens if one of those packs goes then, how long will it take before the other club members jump all over you?

I am not anit-Li-Poly, but there are some serious unresolved issues.

But man do I want that duration!!!!

Ken
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Old Aug 14, 2003, 01:26 PM
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I always try to be precise in my use of language. The word "firsthand" was specifically included because descriptions of similar incidents previous to Dimberio's were best efforts at reconstructing what had happened when someone was out of the room rather than eyewitness accounts.

Preciseness in language is important. Ten people can watch the same thing happen and provide 10 different accounts of what happened. Some of that is due to differences in the way people perceive things and some of it is due to differences in the way people express themselves. When all of the reports are read carefully, a wide variety of descriptions can be seen. Sometimes the cells puff up, sometimes they smoke, sometimes they burn, sometimes they stay in one spot, sometimes they vent and move and, in at least a couple of cases, they appear to have come apart with a violence that is more like what you would expect from a hard-case Li-ion.

It's not easy to sort through all of these various descriptions and try to understand which wording is a variation in someone's perception versus physical differences in the events. But without understanding all of the variables, it's not possible to prepare for and guard against everything that can possibly go wrong.
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Old Aug 14, 2003, 02:03 PM
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There is the age old question "If a tree falls in the forest, and nobody is there to witness it, does it make a sound?"

Now we can add Dave's question, "If a LiPo battery pack burns down your, house, car, garage, kitchen, but nobody is there to witness it does that mean it's not possible to prepare for and guard against everything that can go wrong?"

Dave is it ever "possible to prepare for and guard against everything that can go wrong"? As a human being can you possibly ever know "everything that can possibly go wrong"?

Yes, you are precise, but all knowing????

Brad
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Old Aug 14, 2003, 02:15 PM
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"the more you look, the less you see...
the less you look the more you see"

--song on the radio right now....seems appropriate, for some reason
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Old Aug 14, 2003, 03:18 PM
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Re: Great thread

Quote:
Originally posted by Ken LaPointe
This is really good information and has opened my eyes a bit on changing over to Li-Poly packs.

<lots of good stuff snipped>

I am not anti-Li-Poly, but there are some serious unresolved issues.

But man do I want that duration!!!!

Ken
I'm with you all the way, Ken.

If you're not also chasing the weight saving which lipos bestow on a model, one way to get more duration is to try the GP3300 NiMHs. I've got a couple of zapped 20-cell packs of them which I'm currently flying in a couple of EDFs. They draw 48A peak, falling to about 43-ish during the first minute. Flight times are about 5-6 mins.

Using the same cell packs in my 1/5th scale 70" span 9-1/2lb Tiger Moth, I easily get 20-minute flights in calm conditions. About 17 mins in 20+mph winds. Peak current is 27A. Plane still does good aeros with just one minute's juice left before landing (same for the jets).

I'm now thinking of investing in a couple more of these packs, whilst watching how lipos develop.

Like lipos, they take an hour to charge (you don't charge at faster than 1C or they can overheat), so more than one pack is needed.

Sorry for going off-topic Ken, but your comment ref duration seemed to beg the above comment.

Gordon
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Old Aug 14, 2003, 04:32 PM
BEC
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>>>>>>>The charger was a Shulze. It had the software versopm previous to the one that is now been updated (Version 8) I bought my charger from the US distributor apparently just a month or so before the ones with the updated version. I must say the US distributor was not much help. They refered me to Shulze in Germany where I ended up sending my charred charger for repair and updating. I don't know how many amps were being put in as it was supposed to function automatically.<<<<<<<<

This is unfortunate miscommunication between dimberio, R/C Direct and Schulze. The schulze V8 chargers do not have and will not have any "automatic" function for charging lithium batteries. In V7 they did NiCds automatically ONLY. In V8, they have added auto capability for NiMH (which, in my limited experience, works very well, and allows auto-cycling of NiMH batteries). Even with the upcoming 8.05 software you still MUST SET the number of cells AND THE CHARGE RATE MANUALLY. V8.05 will, as I understand it, check and warn you if it thinks you've mis-set the number of cells. I'll find out when I get my 8.05 EPROMS.

We have two different LiPoly problems going on here, and they overlap.

The first is that charging errors are happening, due to either charger malfunctions, misunderstandings, or just plane operator error. If the cell count the charger is charging is too high or the charger is set for the wrong battery type (as in Melf's story below), batteries WILL be destroyed, perhaps spectacularly as we are seeing.

The second is the crash damage issue. As they are currently being packaged, LiPolys are inherently much more susceptible to crash damage. This aspect worries me enough to wonder what I will do the first time I'm confronted with a crash-damaged pack. I now have my ceramic wall tiles to put the pack on while it's under observation, but I wonder if that is enough. And I'm reconsidering where the Thunderpower 7800 pack that's in my truck right now is going to be riding in case I get in a traffic accident and it goes flying inside the vehicle.
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Old Aug 14, 2003, 07:16 PM
MKH
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Quote:
Originally posted by BEC
The second is the crash damage issue. As they are currently being packaged, LiPolys are inherently much more susceptible to crash damage. This aspect worries me enough to wonder what I will do the first time I'm confronted with a crash-damaged pack.
Same here. I can be accountable for charging and storage matters, but I can't see inside a pack to verify internal conditions after a crash. For now, any less-than-normal arrival will necessitate safe storage and observation of the pack used for that flight. Maybe thats the price for low weight and great performance. I can live with that, as long as its part of my routine.
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Old Aug 14, 2003, 09:25 PM
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Quote:
Originally posted by hoppy
I sure wish I knew if they would fly out of that dish if they ignited. Any reports of flying batteries?
hoppy
Well, I got my answer on the "lipo fire pictures" thread. They will act like rockets. That kind of throws a damper on the 'uncovered' fireproof surface charge station. Here is the post from 'BigDave':

"Caused a house fire also. I posted this several months ago here but obviously, new readers.

I had a Li pack explode while charging and shoot itself off of my charging bench. the pack landed on CARPET in my hobby room and started a fire. The resulting damage to my house was limited as my fire alarm system went off and, luckily, I was there. A fire extinguisher stopped this from turning into a major disaster (like the vehicle in this posting). Several planes and kits went up in smoke. Lots of repairs to the home were required BUT it could have been worse.

The cause was ME. I had my Li charger set for three cells and I connected a two-cell pack. No excuse here.

Nevertheless, ALWAYS charge Li packs in a fire proof contatiner with a LID. If the pack ruptures it will ROCKET off of any fireproof surface and jet off to some other area. This is a cheap lesson for those reading this post. Remember what you saw and take precautions. The packs are wonderful when treated with respect but THEY CAN BITE." http://www.rcgroups.com/forums/showt...ghlight=rocket

Well, I guess it's an ammo box or safe.
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Old Aug 14, 2003, 09:31 PM
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Reading this thread does not make me feel confident about useing and storing lipos. Being new to electrics and lipos has me questioning the wisdom of my battery choices. I am storing my new lipos in a sturdy metal cash box with a lid. Should contain any fires....I hope.
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Old Aug 15, 2003, 12:33 AM
Tight is Right
Darren Hintze's Avatar
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Interesting thread. Thanks for starting it Ken.

I have another incident to report.... in fact... I was coming here specifically to report it when finding this thread.

I have also now blown up and nearly burned a car with lipo packs. My incident can be traced to sheer stupidity, but something to be cautious about.

I use a simple little Hobbico Field Charger MKII to charge my lipo and parkie packs. I generally charge in open and "safe" environments but I will throw my charger on to peak up while I drive to the field.

Well, a few days ago I set up my charger with a KAN pack and a 2s2p surplus cell phone pack to peak before getting in my car. I always carry a large aluminum heat sink to put the packs directly on, so if they do get hot they don't melt or burn anything, I always thought that was enough... maybe it was enough to save my car... Just as I was about to get in and leave, I received a call and went back into the office. 20 minutes go by on the phone.

I go out to find the 2s2p pack completely obliterated, the metal casings melted into the carpet of the floormat. The underside of the jockeybox and beneath the passenger-side covered in a black sludge. The car was filled with smoke.

After venting the car, I checked the charger. Like an idiot, I'd set the KAN cells for Lipo and the Lipo cells for NIMH -- at 2 amps. For those not familiar with the charger, it's a fairly easy mistake to make by simply pushing the wrong buttons the wrong number of times.... anyway...

Boom.

Fortunately for me, the damage was cosmetic and mostly limited to the easily replacable floor mat. But this got me thinking.... what if I'd done this and got in the car? Boom while I'm on the phone is one thing... Boom while I'm driving down the street is quite another.

No more in-car charging... not even short peak stints.

Now, after handling 25% nitromethane for the same hobby over the past 15 years, Li-Po's have a long way to go before scaring me away. I know of more than a few cases of guys torching homes and cars with that stuff. That didn't stop me, neither will this.

Still, I've been far too cavalier about this technology in the past and my attitude has been properly adjusted. I feel lucky my lesson was not as expensive as Ken's... for I was stupid and he was just unlucky.

BTW, I have had NIMH cells blow during charge also. While still capable of doing significant damage, I don't think the material ever reaches sufficient temperature to start common items on fire. That's not to say NIMH and NICAD's are completely safe either, they aren't.
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Old Aug 15, 2003, 12:37 AM
Tight is Right
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Metal Cash box = Very Bad Idea for battery storage.

Many metal boxes can conduct and short your batteries. If you're going to do this, be sure to line the box with non-conductive soft material that will not short the cells if the terminals touch the metal. The liner should also be soft so that the batteries jumbling around won't damage.
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Old Aug 15, 2003, 01:05 AM
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Just doing a little reading (sorry about the consecutive replies) but I found this very interesting....

"Still, the lithium-ion batteries inside consumer electronics pose little fire hazard. They're small, and manufacturers install safety switches in the batteries, ensuring that firing up a laptop computer means nothing more than turning it on. These switches "add to the safety but also add to the cost," Kino****a notes. "

Now this may be just me, but I've never used a lipo for an airplane anywhere near the size nor energy density of the ones in my two Laptops. Not even close. After seeing what that little pack did with just 20mins at 2 amps overcharge, I'm not nearly as confident those Laptop lipos are not a huge lawsuit waiting to happen.

The research on the flame retardant is very encouraging -- although looking at the date I think this additive was encorporated into Lithium-Ion cells a couple of years ago. It'll help with the burst factor, but frankly I bet Ken's post-crash fire was caused not by the pack itself, but by the wires getting red hot during a short.

I've seen that tests with the lipo's I bought... the little solder tabs glow bright red if the pack shorts. Those would start most materials on fire even if the pack chemistry itself is protected.

Unfortunately any short protection would also increase battery resistance and be undesirable for our use.
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